JP3738928B2 - Vertical induction motor rotor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotor of a saddle type induction motor.
[0002]
[Prior art]
A conventional rotor bar of a saddle type induction motor will be described with reference to the drawings.
5 is a front view of a conventional saddle-type induction motor rotor, FIG. 6 is a cross-sectional view taken along the line AA in FIG. 5, FIG. 7 is an enlarged view of a portion B in FIG. 6, 1 is a rotor core, 2 is a rotor bar, 3 is an end ring, and 4 is a shaft.
A plurality of slot grooves 1 a are provided on the outer peripheral side of the rotor core 1 mounted on the shaft 4, and the rotor bars 2 pass through the slot grooves 1 a, respectively. The end ring 3 is brazed and joined.
A gap between the slot groove 1a of the rotor core 1 and the rotor bar 2 is filled with an impregnating resin 5 so that the heat of the rotor bar 2 as a heating element is efficiently transmitted to the rotor core 1 side. .
[0003]
Further, a swaging 2a is applied to the rotor bar 2 at the central portion of the rotor core 1, and the rotor bar 2 is expanded to be fixed to the slot groove 1a, and each rotor bar is stored in the slot groove 1a of the rotor core 1. 2 is fixed so as not to move in the longitudinal direction.
In the conventional method, the length S of the swaging 2a is long and is 80% or more of the length L of the rotor core 1.
That is, since the swaging length and the natural frequency of the rotor bar are in a substantially proportional relationship, the natural frequency can be increased by increasing the swaging length.
[0004]
[Problems to be solved by the invention]
When a saddle type induction motor incorporating a conventional type rotor is driven by a VVVF inverter device, the output frequency of the VVVF inverter device generates a harmonic of 6n (n is a natural number) times in addition to the fundamental wave. As a result, resonance stress is generated in the rotor bar due to the harmonic torque ripple included in the output frequency.
FIG. 8 shows the size H2 and the waveform.
However, it has been found that when a torsional excitation force acts on the rotor of a conventional saddle type induction motor due to the harmonic torque ripple, a very large resonance stress is generated on the rotor bar of the rotor.
That is, in the conventional vertical induction motor rotor, simply by increasing the length of swaging, as described above, when the torsional excitation force acts on the vertical induction motor rotor due to the harmonic torque ripple, A very large resonance stress is generated in the rotor bar of the rotor, and the rotor bar may eventually break near the joint with the end ring.
The present invention has been made in view of the above-described problems. The object of the present invention is to provide a rotor bar for a rotor even if a torsional excitation force acts on the rotor of a saddle type induction motor due to harmonic torque ripple. The rotor of a saddle type induction motor having a swaging length that can reduce the resonance stress generated in the rotor as much as possible and prevent breakage of the rotor bar is provided.
[0005]
[Means for Solving the Problems]
In other words, the means to achieve that purpose is
In a rotor of a saddle-type induction motor having a structure in which a rotor core is mounted on a shaft and a rotor bar is passed through a plurality of slot grooves provided on the outer periphery of the rotor core, The swaging length of the rotor bar is set so that the length of the rotor core exceeds 20% and not more than 40%, and the rotor bar is fixed to the slot groove of the rotor core by swaging within this range.
As a result, even if a torsional excitation force acts on the rotor of the saddle type induction motor due to the harmonic torque ripple included in the output of the VVVF inverter device, the resonance stress generated in the rotor bar of the rotor can be minimized. Can be prevented.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a front view of a saddle type induction motor rotor showing an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is an enlarged view of a portion B in FIG.
In the figure, 6 is a rotor bar, and 6a is a swaging portion applied to the rotor bar 6. In addition, the same code | symbol was attached | subjected to the same part as the prior art shown in FIGS.
In the present invention, the swaging length S applied to the rotor bar 2 is set to be more than 20% and not more than 40% of the iron core length L of the rotor, which is very short with respect to the conventional length. The swaging position may be only one in the central portion in the longitudinal direction of the rotor. If the total length is more than 20% and less than 40% of L, it is divided and provided intermittently at several places. Also good.
[0007]
【The invention's effect】
FIG. 4 shows the state of resonance stress generated in the rotor bar by the harmonic torque ripple included in the output of the VVVF inverter device when the vertical induction motor incorporating the rotor of the present invention is driven by the VVVF inverter device. Therefore, the maximum value H1 of the resonance stress is significantly smaller than the maximum value H2 of the resonance stress in the case of the conventional swaging length shown in FIG. Further, according to the method of the present invention, the waveform itself exhibits a nonlinear vibration waveform in which the resonance phenomenon disappears instantaneously after reaching the maximum amplitude H1, and from this point also, the duration of the resonance stress generated in the rotor bar is conventionally Compared to this method, the time is shorter, and therefore the number of repetitions of the resonance stress acting on the rotor bar is reduced. Therefore, it was confirmed that the method is extremely effective for preventing breakage of the rotor bar.
In addition, shortening the swaging length has made it possible to significantly reduce the work time.
[Brief description of the drawings]
FIG. 1 is a front view of a saddle type induction motor rotor showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is an enlarged view of a portion B in FIG. 2;
FIG. 4 is a waveform diagram of resonance stress generated in a rotor bar when a saddle type induction motor to which the present invention is applied is driven by a VVVF inverter device.
FIG. 5 is a front view of a conventional saddle type induction motor rotor.
6 is a cross-sectional view taken along the line AA in FIG.
7 is an enlarged view of part B in FIG. 6;
FIG. 8 is a waveform diagram of resonance stress generated in a rotor bar when a conventional saddle type induction motor is driven by a VVVF inverter device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotor core 1a Slot groove 2 Rotor bar 2a Swaging 3 End ring 4 Shaft 5 Impregnation resin 6 Rotor bar 6a Swaging

Claims (1)

In a rotor of a vertical induction motor having a structure in which a laminated rotor core is mounted on a shaft and a rotor bar is inserted through a plurality of slot grooves provided on the outer periphery of the rotor core, the rotor core The rotor bar swaging length in the center is formed to be more than 20% and 40% or less of the length of the rotor core, and the rotor bar is fixed to the slot groove of the rotor core by swaging within this range. A rotor of a saddle type induction motor characterized by having been made.

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